DESCRIPIION(provided by applicant)Sensory vestibular signals are transformed in the vestibular nuclei aboutn a vartety of ways. The nature of transformation depends on the type of vestibular nucleus neuron and the behavioral context. The goals of proposed studies are 1) to determine the dynamic characteristics and coordinate frame(s) of the angular linear self-motion signals carried by vestibulo-thalamic pathways and 2) to determine how these self-mo about signals change as a function of behavioral context. Single unit recordings will be obtained fi orthodromically identified secondary vestibular neurons that project to the thalamus. The focus will be units whose firing behavior is related to horizontal rotation and/or translation in the horizontal plane. interaction of vestibular signals with visual self-motion signals will be studied by comparing unit response passive movement in the dark with responses evoked in a lighted surround or during viewing of target, different distances. The interaction of vestibular signals with proprioceptive estimates of self-motion wil] studied by comparing unit responses to passive movement in the dark with responses evoked when the hea about held stable in space and the body is moved, or the platform that serves as the support surface is moved. 1 self motion signals produced by vestibulo-thalamic neurons during passive and active movements will compared signals produced during smooth tracking head movements. Different combinations of act rotational and translational head movements will be examined. In some conditions the head will be free move in the plane of the horizontal semicircular canal and in others it will be restrained from moving respect to the body or with respect to the turntable. The results will add to our fundamental understandin about how multimodal sensory signals are integrated in ascending vestibular sensory pathways, and how they modified in different behavioral contexts. Such knowledge should be useful in the development countermeasures for the profound changes in sensory processing of vestibular sensory information in elde people who suffer from a progressive loss of vestibular function.